Recurrent and metastatic head and neck squamous cell carcinoma (HNSCC) is incurable and causes frequent functional disability and high mortality.6 Clinical trials have demonstrated promising clinical efficacy of anti-programmed death-1 (PD-1) therapy in HNSCCs, and nivolumab and pembrolizumab have been currently approved for HNSCC refractory to platinum-based therapy.7–9 However, the response rates of these immunotherapies are relatively low (13‒16%), and progression-free survival is limited in the majority of patients. This evidence concerns the gene PDCD1 and head and neck squamous cell carcinoma.